1. Field of the Invention
This invention relates to novel anionic Group VIII metal hydrides, containing organoligands of the Group V elements of phosphorus, arsenic and antimony, and methods for their preparation, said hydrides being useful as catalysts for the hydrogenation of aldehydes, ketones, olefins and alkynes.
2. Brief Description of the Background of the Invention Including Prior Art
Main group metallic hydrides, such as lithium aluminum hydride, are well known in the art as excellent reagents for the reduction of a wide variety of unsaturated polar organic substrates such as aldehydes, ketones, carboxylic acid esters and nitriles. The disadvantage of these reagents is that they must be used in at least a stoichiometric quantity to insure high yields of desired products.
Neutral transition metal hydride complexes, such as tris (triphenylphosphine)ruthenium hydridochloride, are known to be useful in catalytic quantities for the hydrogenation of olefins, as described in J. Chem. Soc. (A) 3143 (1968) and for the oligomerization of ethylene and butadiene as described in J. Catalysis 27, 442 (1972).
A variety of metal hydride type compositions which would be able to function in catalytic quantities in the presence of gaseous hydrogen, are increasingly desired in the art for the catalyzed hydrogenation of a wide variety of unsaturated organic compounds such as aldehydes, ketones, olefins, alkynes and the like. The use of such catalysts would significantly reduce the cost of reduction reactions since the use of gaseous hydrogen in stoichiometric quantities and the use of a metal hydride in catalytic quantities would be relatively inexpensive as compared to the use of main group metallic hydrides in stoichiometric quantities.
Several anionic transition metal hydride complexes, containing specifically carbonyl ligands, are known, as for example, Na.sup.+ HFe(CO.sub.4).sup.- and [V(CO).sub.5 PPh.sub.3 ].sup.- [Et.sub.4 N].sup.+, described in J. Organomet. Chem. 31, 239 (1971).
Anionic Group VIII metal complex hydrides, containing only ligands of Group V elements, and not carbonyl ligands attached to the metal atom in the molecule, are not well known in the art.
The reference, J. Chem. Soc., 843 (1965) describes the preparation of a ruthenium complex in anionic form, namely, sodium bis(bisdimethylphosphinoethane) ruthenium hydride, Na[RuH(Me.sub.2 PCH.sub.2 CH.sub.2 PMe.sub.2).sub.2 ] which contains four coordinated phosphorus atoms per ruthenium atom. However, the compound was not isolated or characterized and no specific mention is made of its possible usefulness as a catalyst in hydrogenation reactions, i.e. reduction by molecular hydrogen.
The reference, Chemical Communications, pp 857858 (1968), describes the preparation of specifically the ninecoordinate octahydrido(tertiaryphosphine) complex of the Group VII metal rhenium. No specific mention is made of its possible usefulness as a catalyst.